Method of use of an ionic liquid and device for sorption of a gas

ABSTRACT

A method of use of an ionic liquid for sorption of a gas having an electric multipole moment is provided, wherein the ionic liquid comprises an anion and a non-aromatic cation. In particular, the electric multipole moment may be an electric dipole moment and/or an electric quadrupole moment. The sorption may be an adsorption or an absorption. The ionic liquid may be a pure ionic liquid, i.e. a liquid substantially only containing anions and cations, while not containing other components, e.g. water. Alternatively a solution containing the ionic liquid and a solvent or further compound, e.g. water, may be used.

FIELD OF THE INVENTION

The invention relates to a method of use of an ionic liquid, inparticular for sorption of a gas or vapor having an electric multipolemoment.

Further, the invention relates to a device for sorption of a gas orvapor.

BACKGROUND OF THE INVENTION

Carbon dioxide (CO₂) is an undesired diluent that is present in many gassources. In order to improve the quality of the gases the CO₂ should beremoved to acceptable specifications. In gas processing industry,various technologies have been employed for CO₂ removal includingchemical solvents, physical solvents, and membranes. By far, chemicalsolvents that reversibly react with CO₂ are most commonly used for CO₂removal.

Furthermore, processes for removal of CO₂ from gaseous streams areknown, which comprise the contacting a CO₂ containing gaseous streamwith an absorbent comprising from 1 to 20 wt % water and an ionic liquidcomprising pyridines or imidazole cations and an anion, wherein saidcontacting occurs at absorption conditions, to absorb at least a portionof the CO₂ from the CO₂ containing gaseous stream and forming aCO₂-absorbent complex. Afterwards the gaseous product having a reducedCO₂ content is recovered.

However, the known processes of removal CO₂ may be costly.

OBJECT AND SUMMARY OF THE INVENTION

It may be an objective of the invention to provide a method of removalof a gaseous or vaporous component and a device for removal of a gaseousor vaporous component which may be save to use or less expensive thanknown methods.

This object may be solved by a method of use of an ionic liquid, inparticular for sorption of a gas or vapor having an electric multipolemoment and a device for sorption of a gas or vapor according to theindependent claims. Further exemplary embodiments are described in thedependent claims.

According to an exemplary aspect of the invention a method of use of anionic liquid for sorption of a gas having an electric multipole momentis provided, wherein the ionic liquid comprises an anion and anon-aromatic cation. It should be noted that according to thisapplication the terms “gas” and “gaseous” and “vapor” and “vaporous”,respectively may be interchangeably used, i.e. no distinction is madebetween these two terms.

In particular, the electric multipole moment may be an electric dipolemoment and/or an electric quadrupole moment. The sorption may be anadsorption or an absorption. The ionic liquid may be a pure ionicliquid, i.e. a liquid substantially only containing anions and cations,while not containing other components, e.g. water. Alternatively asolution containing the ionic liquid and a solvent or further compound,e.g. water, may be used. For example, the content of other componentsthan the ionic liquid may be 35% or less by mass, in particular lessthan 30% by mass, less than 20% by mass, less than 10% by mass, or evenless than 5% by mass, wherein for all the above ranges the lower limitmay be about 10 ppm. However, in case of water as the other componentthe ranges may be between about 10 ppm and 50% by mass, in particularbetween about 10 ppm and 35% by mass, between about 10 ppm and 20% bymass, between about 10 ppm and 10% by mass, or even between about 10 ppmand 5% by mass. In this context it should be noted that according tospecific embodiments the sorption may be performed by the ionic liquiditself, e.g. may particularly be a physical sorption. In general, theionic liquid may also perform a chemical sorption, a physical sorptionor a combined chemical-physical sorption. This process has to bedistinguished from a process in which the ionic liquid only forms asolvent for a compound or component, e.g. a polymer, which then acts asthe sorbent for the gas having an electric multipole moment. That is,according to specific embodiments of the invention the ionic liquid mayform the sorbent which sorbs the gas having an electric multipolemoment. Consequently a method according to an exemplary embodiment maycomprise the step of sorbing a gas having an electric multipole momentby an ionic liquid, wherein the ionic liquid may be a pure orsubstantially pure ionic liquid or may include some additives havingonly few, e.g. less than 35% by mass, further components. In the mostgeneric form the ionic liquids may be represented by [Q⁺]_(n)[Z^(n-)],wherein Q represents a non-aromatic cation and which may be produced bya process as described for example in WO 2005/021484 which is herebyherein incorporated by reference.

According to an exemplary aspect of the invention a device for sorptionof a gas having an electric multipole moment is provided, wherein thedevice comprises a reservoir of an ionic liquid comprising an anion anda non-aromatic cation.

In particular, the device may comprise an inlet, a container includingthe ionic liquid, and optionally an outlet. The device may be used tosorb gas having an electric multipole moment, e.g. CO₂, from a mediumwhich is selected out of the group consisting of recovery gas, synthesisgas, water gas, natural gas, inhaled air, and exhaled air. Inparticular, the device may be a heat pump. The heat pump may comprise acircuit including CO₂ and the ionic liquid which comprises an anion anda non-aromatic cation as working media. In particular, the usage of apair of working media containing CO₂ and an ionic liquid in a heat pumpmay be advantageous since CO₂ is not toxic is of less concern withrespect to environmental effect compared to other vaporizable workingsubstances.

According to an exemplary aspect of the invention a method of use of anionic liquid for sorption of a gas having an electric multipole momentis provided, wherein the ionic liquid comprises a carbanion and acation.

The use of non-aromatic cations of the ionic liquid may provide for anionic liquid which may be cheaper and more secure than the use ofaromatic cations. Such ionic liquids may be a suitable medium to sorbspecific gases, e.g. CO₂, or vapor out of a mixture of gases and mayalso be suitable to release these specific gases or vapor again. Thespecific gases and the ionic liquid may form a complex, i.e. thespecific gases may be complex bound. According to some exemplaryembodiments it may even be possible to remove the complex bound in theform of a solid compound. The uses of such ionic liquids for sorption ofgases may be advantageous since ionic liquids may be used showing no orat least substantially no vapor pressure, e.g. a non measureable vaporpressure or even a vapor pressure in the same magnitude of order ofsteel. Thus, the gases or mixture of gases may not be contaminated byvapor of the ionic liquid. Furthermore, the use of non-aromatic ionicliquids may increase the performance of the sorption process compared tothe case in which aromatic ionic liquids are used. For example, theremoval of CO₂ by using non-aromatic ionic liquids may exhibit animproved performance even in cases where the vapor pressure of CO₂ islow.

However, alternatively it may also be possible to use an ionic liquidhaving aromatic cation in case the ionic liquid comprises a carbanion.That is, when using an ionic liquid comprising a carbanion the cationmay be an aromatic or a non-aromatic anion.

Next, further aspects of exemplary embodiments of the method of use ofan ionic liquid for sorption of a gas are described. However, theseembodiments also apply for the device for sorption of a gas.

According to an exemplary embodiment of the method of use of an ionicliquid the non-aromatic cation is an aliphatic cation. The term“aliphatic cation” may also include cations having aliphatic sidechains.

Aliphatic cations may be suitable non-aromatic cations for an ionicliquid which are less expensive and/or less toxic than typical aromaticcations.

According to an exemplary embodiment of the method of use of an ionicliquid the ionic liquid satisfy the generic formula [Q⁺][A⁻],

wherein the anion can be described by one of the following structures:

In particular, the anion may be describable by the resonant or mesomericstates:

wherein X and Y may indicate, independently from each other, groupswhich may attract electrons due to the inductive effect or the mesomericeffect and/or which may delocalize and/or stabilize (localize)electrons. Examples for such groups may be:

-   -   —CN, —NO₂, —NO₃, —CO—R^(k), —COOR^(k), —C═N—R^(k),        —CO—NR^(k)R^(m), —NR^(k)R^(m), —OH, —OR^(k), —SH, —SR^(k),        —SO—R^(k), —SO₂—R^(k), —SO₂—OR^(k), —PO—OR^(k)OR^(m)        (phosphonate), —I, —Cl, —Br, —F, —CCl₃, —CCl₂R^(k),        —CClR^(k)R^(m), —CF₃, —CF₂R^(k), —CFR^(k)R^(m), —SO₂CF₃,        —COOCF₃, —C₆H₅, —CR^(k═CR) ^(m)R^(n), —C≡CR^(m),        CR^(k)═CR^(m)—CN, —CR^(k)═CR^(m)—NO₂, —CR^(k)═CR^(m)—CO—R^(k),        —CR^(k)═CR^(m)—COOR^(k), —CR^(k)═CR^(m)—C═N—R^(n),        —CR^(k)═CR^(m)—CO—NR^(n)R^(o), —CR^(k)═CR^(m)—NR^(n)R^(o),        —CR^(k)═CR^(m)—OR^(n), —CR^(k)═CR^(m)—SR^(n),        CR^(k)═CR^(m)—SO—R^(n), —CR^(k)═CR^(m)—SO₂—R^(n),        —CR^(k)═CR^(m)—SO₂—R^(n), —CR^(k)═CR^(m)—SO₂—OR^(n),        —CR^(k)═CR^(m)—CF₃, —CR^(k)═CR^(m)—SO₂CF₃,        wherein R^(k), R^(m), R^(n), R^(o) may, independently from each        other, denote hydrogen, C₁- to C₃₀-alkyl and their aryl-,        heteroaryl-, cycloalkyl-, halogen-, hydroxy-, amino-, carboxy-,        formyl-, —O—, —CO—, —CO—O— or —CO—N< substituted components,        like methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl,        2-methyl-1-propyl (isobutyl), 2-methyl-2-propyl (tert.-butyl),        1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl,        3-methyl-1-butyl, 2-methyl-2-butyl, 3-methyl-2-butyl,        2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl, 3-hexyl,        2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl,        2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl,        2-methyl-3-pentyl, 3-methyl-3-pentyl, 2,2-dimethyl-1-butyl,        2,3-dimethyl-1-butyl, 3,3-dimethyl-1-butyl, 2-ethyl-1-butyl,        2,3-dimethyl-2-butyl, 3,3-dimethyl-2-butyl, heptyl, octyl,        nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl,        pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl,        henicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl,        heptacosyl, octacosyl, nonacosyl, triacontyl, phenylmethyl        (benzyl), diphenylmethyl, triphenylmethyl, 2-phenylethyl,        3-phenylpropyl, cyclopentylmethyl, 2-cyclopentylethyl,        3-cyclopentylpropyl, cyclohexylmethyl, 2-cyclohexylethyl,        3-cyclohexylpropyl, methoxy, ethoxy, formyl, acetyl or        C_(n)F_(2(n−a)+(1−b))H_(2a+b) wherein n≦30, 0≦a≦n and b=0 or 1        (e.g. CF₃, C₂F₅, CH₂CH₂—C_((n−2))F_(2(n−2)+1), C₆F₁₃, C₈F₁₇,        C₁₀F₂₁, C₁₂F₂₅);

C₃- to C₁₂-cycloalkyl and their aryl-, heteroaryl-, cycloalkyl-,halogen-, hydroxy-, amino-, carboxy-, formyl-, —O—, —CO— or—CO—O-substituted components, e.g. cyclopentyl, 2-methyl-1-cyclopentyl,3-methyl-1-cyclopentyl, cyclohexyl, 2-methyl-1-cyclohexyl,3-methyl-1-cyclohexyl, 4-methyl-1-cyclohexyl orC_(n)F_(2(n−a)−(1−b))H_(2a−b) wherein n≦0, 0≦a≦n and b=0 or 1;

C₂- to C₃₀-alkenyl and their aryl-, heteroaryl-, cycloalkyl-, halogen-,hydroxy-, amino-, carboxy-, formyl-, —O—, —CO— or —CO—O-substitutedcomponents, e.g. 2-propenyl, 3-butenyl, cis-2-butenyl, trans-2-butenylor C_(n)F_(2(n−a)−(1−b))H_(2a−b) wherein n≦30, 0≦a≦n and b=0 or 1;

C₃- to C₁₂-cycloalkenyl and their aryl-, heteroaryl-, cycloalkyl-,halogen-, hydroxy-, amino-, carboxy-, formyl-, —O—, —CO— or—CO—O-substituted components, e.g. 3-cyclopentenyl, 2-cyclohexenyl,3-cyclohexenyl, 2,5-cyclohexadienyl or C_(n)F_(2(n−a)−3(1=b))H_(2a−3b)wherein n≦0, 0≦a≦n and b=0 or 1; and

aryl or heteroaryl having 2 to 30 carbon atoms and their alkyl-, aryl-,heteroaryl-, cycloalkyl-, halogen-, hydroxy-, amino-, carboxy-, formyl-,—O—, —CO— or —CO—O-substituted components, e.g. phenyl, 2-methyl-phenyl(2-tolyl), 3-methyl-phenyl (3-tolyl), 4-methyl-phenyl, 2-ethyl-phenyl,3-ethyl-phenyl, 4-ethyl-phenyl, 2,3-dimethyl-phenyl,2,4-dimethyl-phenyl, 2,5-dimethyl-phenyl, 2,6-dimethyl-phenyl,3,4-dimethyl-phenyl, 3,5-dimethyl-phenyl, 4-phenyl-phenyl, 1-naphthyl,2-naphthyl, 1-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 2-pyridinyl,3-pyridinyl, 4-Pyridinyl or C₆F_((5−a))H_(a) wherein 0≦a≦5,

wherein pairs of the R^(k), R^(m), R^(n), R^(o) may be bonded directlyto each other or via C₁-C₄, which may be substituted if necessary, sothat a saturated, unsaturated, or conjugated unsaturated ring may beformed.

According to an exemplary embodiment of the method of use of an ionicliquid the ionic liquid satisfy the generic formula [Q⁺]_(a)[A^(a-)],wherein [A^(a-)] with the charge a- is selected out of the groupconsisting of:

dialkyl ketones, dialkyl-1,3-diketones, alkyl-β-keto esters, terminalalkines, linear or cyclic 1,3-thioethers, dialkyl phosphonates, dialkylmalonic acid esters, β-cyano carbonic acids and their respectivealkylesters, β-alkoxy carbonic acids and their respective alkylesters,β-cyano nitriles, cyclopentadiene (substituted if necessary),trialkylimines, dialkylimines, diaryl ketones, alkyl-aryl-ketones,diary)-1,3-diketones, alkyl-aryl-1,3-diketones, β-aryloxy carbonic acidsand their respective alkylesters, β-aryloxy carbonic acids and theirrespective arylesters, aryl-β-ketoesters, diarylphosphonates,alkyl-aryl-phosphonates, diaryl malonic acid esters, alkyl-aryl-malonicacid esters, β-cyano carbonic acids arylesters and arylimines.

According to an exemplary embodiment of the method of use of an ionicliquid the ionic liquid satisfy the generic formula[Q⁺]_(a)[A^(a-],wherein [A) ^(a-)] is a carbanion formed bydeprotonating a chemical compound out of the group consisting of:

acetoacetic ester, malonic mononitrile, malonic acid dimethylester,malonic acid diethylester, acetylacetone, malonic acid dinitrile,acetone, diethylketone, methlethylketone, dibutylketone, 1,3-dithian,acetaldehyde, benzaldehyde, crotonaldehyde and butyraldehyde.

According to an exemplary embodiment of the method of use of an ionicliquid the ionic liquid satisfy the generic formula [Q⁺]_(a)[A^(a-)],wherein [A^(a-)] is a carbanion and wherein [C]⁺ is one out of the groupconsisting of quaternary ammonium cation [R^(1′)R¹R²R³N]⁺, phosphonium[R^(1′)R¹R²R³P]⁺, sulfonium [R^(1′)R¹R²S]⁺ and a hetero aromatic cation.In particular, the carbanion may be formed by deprotonating a chemicalcompound out of the group consisting of: acetoacetic ester, malonicmononitrile, malonic acid dimethylester, malonic acid diethylester,acetylacetone, malonic acid dinitrile, acetone, diethylketone,methlethylketone, dibutylketone, 1,3-dithian, acetaldehyde,benzaldehyde, crotonaldehyde and butyraldehyde.

In particular:

R¹, R^(1′), R², R³ may be alkyl, alkenyl, alkinyl, cycloalkyl,cycloalkenyl, aryl or heteroaryl which may be independently substituted,or

two of the moieties R¹, R^(1′), R², R³ may form a ring together with ahetero-atom to which they are bound. The ring may be saturated,unsaturated, substituted or unsubstitued. The chain may be interruptedby one or more hetero-atoms out of the group consisting of O, S, NH orN—C₁-C₄-alkyl.

The hetero aromatic cation may be a 5 or 6 membered ring comprising atleast one N and if necessary one 0 and/or one S. The hetero aromaticcation may be substituted or unsubstituted and/or annelated. Preferably,the hetero aromatic cation is selected from the group consisting of:

wherein the moieties R may be one of the following:

R hydrogen, C₁-C₃₀-alkyl, C₃-C₁₂-cycloalkyl, C₂-C₃₀-alkenyl,C₃-C₁₂-cycloalkenyl, C₂-C₃₀-alkinyl, aryl or heteroaryl, wherein thelatter 7 moieties may have one or more halogenic moiety and/or 1 to 3moieties selected from the group consisting of C₁-C₆-alkyl, aryl,heteroaryl, C₃-C₇-cycloalkyl, halogen, OR^(c), SR^(c), NR^(c)R^(d),COR^(c), COOR^(c), CO—NR^(c)R^(d), wherein R^(c) and R^(d) may behydrogen, C₁-C₆-alkyl, C₁-C₆-halogenalkyl, cyclopentyl, cyclohexyl,phenyl, tolyl or benzyl;

R¹, R^(1′), R², R³ may be hydrogen, alkyl, alkenyl, alkinyl, cycloalkyl,cycloalkenyl, aryl or heteroaryl which may be independently substituted;or

two of the moieties R1, R1′, R2, R3 may form a ring together with ahetero-atom to which they are bound. The ring may be saturated,unsaturated, substituted or unsubstitued. The chain may be interruptedby one or more hetero-atoms out of the group consisting of O, S, NH orN—C₁-C₄-alkyl;

R⁴, R⁵, R⁶, R⁷, R⁸ may be, independently of each other, hydrogen,halogen, nitro, cyano, OR^(c), SR^(c), NR^(c)R^(d), COR^(c), COOR^(c),CO—NR^(c)R^(d), C₁-C₃₀-alkyl, C₃-C₁₂-cycloalkyl, C₂-C₃₀-alkenyl,C₃-C₁₂-cycloalkenyl, aryl or heteroaryl, wherein the latter 6 moietiesmay comprise one or more halogenic moiety and/or 1 to 3 moietiesselected out of the group consisting of C₁-C₆-alkyl, aryl, heteroaryl,C₃-C₇-cycloalkyl, halogen, OR^(c), SR^(c), NR^(c)R^(d), COR^(c),COOR^(c), CO—NR^(c)R^(d), wherein R^(c) and R^(d)R^(d) may be,independently of each other, hydrogen, C₁-C₆-alkyl, C₁-C₆-halogenalkyl,cyclopentyl, cyclohexyl, phenyl, tolyl or benzyl; or

two neighboring moieties of the moieties R, R⁴, R⁵, R⁶, R⁷, R⁸, mayform, together with an atom they are bound, a ring which may beunsaturated or aromatic, unsaturated or saturated, wherein the chainformed by the respective moieties may be interrupted by one or morehetero-atoms out of the group consisting of O, S, NH or N—C₁-C₄-alkyl;

R^(e), R^(f), R^(g), R^(h) may be, independently of each other,hydrogen, C₁-C₆-alkyl, aryl-, heteroaryl-, C₃-C₇-cycloalkyl, halogen,OR^(c), SR^(c), NR^(c)R^(d), COOR^(c), CO—NR^(c)R^(d) or COR^(c),wherein R^(c), R^(d), may be, independently of each other, hydrogen,C₁-C₆-alkyl, C₁-C₆-halogenalkyl, cyclopentyl, cyclohexyl, phenyl, tolylor benzyl; preferably for hydrogen, halogen, C₁-C₆-alkyl, in particular,hydrogen or C₁-C₆-alkyl.

According to an exemplary embodiment of the method of use of an ionicliquid the non-aromatic cation is a quaternary material. In particular,the quaternary material may be a quaternary salt. Alternatively, the nonaromatic cation may comprise or may consist of protonated bases.

According to an exemplary embodiment of the method of use of an ionicliquid the gas is one out of the group consisting of: H₂O, HCN, H₂S,H₂Se, H₂Te, CO₂, CO, CS₂, COS, CF₂O, CF₂S, O₃, NO, NO₂, N₂O, N₂O₃, NOCl,NF₃, HNO₂, HNO₃, RCOR′, RCOH, RCOOH, CF₃SO₃H, CF₃COOH, RCOOR′, ROH, ROR(including cyclic ethers like tetrahydrofuran), RSH, RSR (includingcyclic thioethers like tetrahydrothiophen), ROCl, ROBr, RONH₂, RONHR',RONR′R″, RSO₂Cl, RSO₂Br, ROCN, RCON, RCN, HF, HCl, HBr, HI, SO₂, SO₃,NH₃, NH₂R, NHR′R″, NR′R″R′″, PH₃, PH₂R, PHR′R″, PR′R″R′″, BF₃, BCl₃,BBr₃, B₂H₆, BrF₃, ClF₃, ClF₅, ClCN, IF_(S), AsH₃, CH₃F, CH₃Cl, CH₃Br,CH₃I, POCl₂, PSCl₂, PF_(S), SF₄, SF₆, SO₂F₂, SO₂Cl₂, SOCl, H₂C═CHBr,H₂C═CHCl and ethylene oxide. In general, every gas or vapor having amultipole moment and which may be classified as an harmful substance,irritant, or toxic substance, e.g. (strong) acids, (strong) bases, maybe sorbed by using a method according to an exemplary embodiment of theinvention. In particular, the sorption process may be used to removethese gases or vapors from air which is inhaled or exhaled.

According to an exemplary embodiment of the method of use of an ionicliquid at least one of R, R′, R″ and/or R′″ is a moiety out of the groupconsisting of: C₁-C₈-alkyl, alkenyl, alkinyl, cycloalkyl, cycloalkenyl,aryl and heteroaryl. In particular, R, R′, R″ and/or R′″ may denote amoiety or radical which may be partially and/or independentlysubstituted. For clarity reasons it should be mentioned that in thisapplication the term C₁-C₈-alkyl or similar terms is an abbreviatorynotation for C1-alkyl, C2-alkyl, . . . , up to C8-alkyl or similarterms.

According to an exemplary embodiment of the method of use of an ionicliquid the anion comprises a carbonate, an alkylcarbonate, anarylcarbonate, alkylcarbonate, carboxylate, a carbanion, and/or anaromatic compound. In particular, the carbonates may be alkaline metalcarbonates, alkaline earth metal carbonates, quaternarytetraalkylammonium carbonates, quaternary tetraalkylphosphoniumcarbonates, hydrogencarbonate, and/or arylcarbonate, for example. Inparticular, the arylcarbonate may be phenylcarbonate or benzylcarbonate,for example.

According to an exemplary embodiment of the method of use of an ionicliquid the anion comprises at least one polar group.

In particular, the polar group may be formed by an acetate, a sulfonate,a sulfate, a carbonate, and/or a malonate compound. Furthermore, itshould be noted that the anion may be polar. In particular, the anionmay be formed by a small ion having a high charge density or by an ion,carrying a functional group with a heteroatom with a high charge densitye.g. O, N, F.

According to an exemplary embodiment of the method of use of an ionicliquid the cation is a quaternary or protonated cation out of the groupconsisting of ammonium, phosphonium, sulfonium, piperidinium,pyrrolidinium and morpholinium.

According to an exemplary embodiment of the method of use of an ionicliquid the cation is one out of the group consisting oftrialkylmethylammonium, tetramethylammonium, triethylmethylammonium,tributylmethylammonium, and trioctylmethylammonium, trialkylammonium,trimethylammonium, triethylammonium, tributylammonium, andtrioctylammonium. In particular, the trialkylmethylammonium may be aC₁-C₁₀-trialkylmethylammonium.

According to an exemplary embodiment of the method of use of an ionicliquid the cation is one out of the group consisting oftetramethylammonium, triethylmethylammonium, tributylmethylammonium, andtrioctylmethylammonium.

According to an exemplary embodiment of the method of use of an ionicliquid the anion can be written in the form [RCO₂ ⁻], wherein [RCO₂ ⁻]is one out of the group consisting of carboxylate, formiate, acetate,propionate, butyrate, benzoate, and salicylate.

According to an exemplary embodiment of the method of use of an ionicliquid the anion can be written in the form [RCO₂ ⁻], wherein [RCO₂ ⁻]is a carboxylate and wherein R is a radical out of the group consistingof C₁-C₃₀-alkyl, C₃-C₁₂-cycloalkyl, C₂-C₃₀-alkenyl, C₃-C₁₂-cycloalkenyl,C₂-C₃₀-alkinyl, aryl and heteroaryl. In particular, the moiety orradical R may comprise or include one or more halogen radicals.

According to an exemplary embodiment of the method of use of an ionicliquid the anion can be written in the form [RCO₂ ⁻], wherein [RCO₂] isa carboxylate wherein R represents one to three radicals out of thegroup consisting of, C₁-C₆-alkyl, aryl, heteroaryl, C₃-C₇-cycloalkyl,halogen, cyanide, ORc, SRc, NRcRd, CORc, COORc, CO—NRcRd, wherein Rcand/or Rd, is one of the group consisting of hydrogen, C₁-C₆-alkyl,C₁-C₆-halogenalkyl, cyclopentyl, cyclohexyl, phenyl, tolyl, and benzyl.

According to an exemplary embodiment of the method of use of an ionicliquid the gas is CO₂.

Summarizing, according to an exemplary aspect of the invention, a methodof use is provided which uses an ionic liquid having a non-aromaticcation to sorb gases having an electric multipole moment. The gas may inparticular be CO₂ while the ionic liquid may be an organic salt having amelting temperature of below 200° C., preferably below 100° C. Theorganic salts may be quaternary salts having a generic formula of:[K⁺][RCO₂]. The described method of use may be in particular useful forall processes in which CO₂ shall be removed as pure substance or from agas or vapor mixture independent of whether CO₂ is a main or secondarycomponent, a process gas, or a working medium. Some exemplaryapplications may be the use in a heat pump or refrigerator based onionic liquid/CO₂ as working media, or removing of CO₂ out of recoverygas, synthesis gas, water gas, inhaled air, and exhaled air. Theremoving out of inhaled/exhaled air may be in particular useful in thefield of aerospace, submarines, or building services engineering whereinthe very low vapor pressure if the ionic liquid may be advantageoussince the ionic liquid may not evaporate into the air. Furthermore, itmay be possible to use ionic liquids which selectively remove CO₂ whiledo not remove water or water vapor, i.e. hydrophobic ionic liquids maybe used. Another possible application may be the purification of CO₂and/or non-pressurized storing of CO₂, since the ionic liquid forms acomplex bound with the quadrupolaric CO₂ which complex bound may bebroken by heating, microwave, ultrasonic wave, or by adding bipolarsolvents, e.g. water, alcohol, etc. In general, every gas or vaporhaving a multipole moment and which may be classified as an harmfulsubstance, irritant, or toxic substance, e.g. (strong) acids, (strong)bases, may be sorbed by using a method according to an exemplaryembodiment of the invention. In particular, the sorption process may beused to remove these gases or vapor from air which is inhaled orexhaled, e.g. for purifying breathable air.

The aspects defined above and further aspects of the invention areapparent from the examples of embodiment to be described hereinafter andare explained with reference to these examples of embodiment. It shouldbe noted that features described in connection with one exemplaryembodiment or exemplary aspect may be combined with other exemplaryembodiments and other exemplary aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail hereinafter withreference to examples of embodiment but to which the invention is notlimited.

FIG. 1 schematically illustrates a heat pump.

FIG. 2 schematically illustrates a test arrangement for measuring a gassorption.

FIG. 3 schematically illustrates a test arrangement for measuringequilibrium curves.

FIG. 4 illustrates equilibrium curves for monoethanolamine.

FIG. 5 illustrates equilibrium curves for choline carbonate.

DESCRIPTION OF EMBODIMENTS

The illustration in the drawing is schematically.

FIG. 1 schematically shows a heat pump which may use a process accordingto an exemplary embodiment, i.e. a process which may be based on pair ofworking media comprising CO₂ and an ionic liquid comprising anon-aromatic ionic liquid.

In particular, FIG. 1 shows a heat pump 100 having an absorber 101,including the pair of working media, e.g. CO₂ and the ionic liquid,wherein the ionic liquid acts as a sorbent and CO₂ is the sorbat. Themixture is transmitted via a pump 102 to a heat exchanger 103 a in whichthe mixture absorbs heat or releases heat. After the heat exchanger themixture is transmitted to a settler 104 in which at least a partiallyseperation of the mixture into a sorbent rich phase and a sorbat richphase is performed. The sorbant rich phase is transferred to transferredtrough a second heat exchanger 103 b and a restrictor 105 a into aevaporizer 106. In the evaporizer 106 the sorbat at least partiallyevaporates out of the sorbat rich phase which is then introduced backinto the absorber 101. Optionally, the sorbat rich phase may be passedthrough another heat exchanger, e.g. heat exchanger 103 b, before it isintroduced into the absorber. The sorbent richt phase is transferredfrom the settler 104 to the absorber 101 via a second restrictor 105 bin which it is brought back to the pressure level of the absorber 100.Optionally the sorbent rich phase may be passed through another heatexchanger, e.g. heat exchanger 103 a, before it is introduced into thesecond restrictor 105 b.

The described heat exchanger is only an example for a device using amethod of use according to an exemplary embodiment of the invention. Aplurality of embodiments may become apparent for a person skilled in theart. For example, a ionic liquid having a non-aromatic cation may beused in a open device, i.e. a device which does not include the ionicliquid in a closed loop, in order to enable the sorption of a gas havingan electric multipole moment.

In the following some experimental results are described showing theability of ionic liquid to absorb CO₂.

FIG. 2 schematically shows a fluid tank 200 used as a heat reservoir inorder to provide a constant temperature selectable in the range between25° C. and 80° C. A vessel or vial 201 having a volume of about 20 ml isplaced in the tank, wherein the vial is filled with CO₂ at a partialpressure of the enviromental pressure, e.g. atmospheric pressure ofabout 1000 hPa. Additionally, a CO₂ sorbing fluid is injected 202 intothe vial. The sorption of the CO₂ is determined by measuring thedecrease of the pressure in the vial by a digital manometer 203 which isconnected to a computer. The speed of the pressure decrease is anindicator of the reaction kenetics and the total decrease of thepressure is an indicator for the total CO₂ sorption. The tests wereperformed at two temperatures 25° C. and 80° C., wherein at the highertemperature a smaller amount of CO₂ may be desirable since this may bean indicator for an estimation of the ability of the fluid to releasethe CO₂. For testing several ionic liquids are injected and compared toa reference sample, wherein an aqueous solution (30%) ofmonoethanolamine is used. In particular, the resulting parameter was theequilibrium concentration at constant reduced pressure, i.e. thepressure reached in the vial, and at the set temperature, wherein theresult was calculated in mol_(gas) per mol_(IL), wherein the index gasdenotes CO₂ and the index IL denotes ionic liquid. The equilibriumconcentration were calculated by the following formular:

$\frac{{pressure}\mspace{14mu} {{{decrease}\mspace{14mu}\lbrack{hPa}\rbrack} \cdot {0.02145\;\lbrack l\rbrack}}}{83.145 \cdot {{temp}\lbrack K\rbrack}}/\frac{{mass}\mspace{14mu} {of}\mspace{14mu} {{CO}_{2}\mspace{14mu}\lbrack g\rbrack}}{{molar}\mspace{14mu} {{mass}\mspace{14mu}\left\lbrack {g\text{/}{mol}} \right\rbrack}}$

wherein 0.02145 is the volume of the vial and 83.145 is the gas constantin the used units.

The following results were achieved:

pressure conc. T decrease time charging name solvent [%] [° C.] [hPa][min] [mol_(CO2)/mol_(IL)] TBMP- 100 25 332 4000 0.08 acetate TBMP- 10080 342 3160 0.08 acetate TEMA- H₂O 70 25 495 2400-5000 0.1 acetate TEMA-H₂O 70 80 130 2400 0.03 acetate TOMA- 100 25 448 2500 0.19 acetate TOMA-100 80 122 1000 0.05 acetate MEA H₂O 30 25 679 250 0.12 MEA H₂O 30 80440 130 0.08 wherein: TBMP denotes tributyl methyl phosphonium, TEMAdenotes triethyl methyl ammonium, TOMA denotes trioctyl methyl ammonium,and MEA denotes monoethanolamine.

As can be seen the acetate anion may be responsible for a high CO₂sorption, while similar sorption amounts may be achievable by cationshaving different structures.

FIG. 3 schematically illustrates a test arrangement 300 for measuringequilibrium curves. In particular, FIG. 3 shows an equilibrium cellcomprising three vessels 301, 302 and 303 each closed by a respectivefrit in order to ensure a good mass transfer between the gas, e.g. CO₂and the sorbing fluid. The vessels are interconnected by flexibleplastic tubes 304 and 305 having non-return valves. The vessels areplaced in a heat reservoir 306 to ensure a constant temperature whichcan be controlled by using an electric heating 307. The heat reservoiris covered by a cover or lid 308 in order to ease the temperaturecontrol. A container or condenser 309 including silica gel isimplemented downstream of the equilibrium cell wherein the silica gel isused to dry the generated gas which is then analyzed. Additionally, aninput amount or volume to the equilibrium cell is controlled orregulated by using a rotameter 310.

FIG. 4 illustrates equilibrium curves for monoethanolamine. Inparticular, FIG. 4 shows the partial pressure p_(CO2) versus the CO₂loading for 60° C. and 80° C. for an aqueous solution (30%) ofmonoethanolamine. For each temperature a respective curve isapproximated based on measurements, wherein a first curve 401approximates the equilibrium curve for 80° C. while a second curve 402approximates the equilibrium curve for 60° C. The values generated forMEA are comparable with the data published in literature, known to theexpert.

FIG. 5 illustrates equilibrium curves for choline carbonate. Inparticular, FIG. 5 shows values for the partial pressure p_(CO2) versusthe CO₂ loading for six different temperatures 40° C., 60° C., 80° C.,90° C., 100° C., and 110° C. for an aqueous solution (60%) of cholinecarbonate. Additionally, to the measured values fits for the differenttemperatures are shown in FIG. 5 as well. In particular, graph 501 showsthe fit for 40° C., graph 502 shows the fit for 60° C., graph 503 showsthe fit for 80° C., graph 504 shows the fit for 90° C., graph 505 showsthe fit for 100° C., and graph 506 shows the fit for 110° C.

Furthermore, an experiment concerning the influence of water on the CO₂sorption was performed. TEMA acetate having a water amount of 10% wasused as an ionic liquid. TEMA acetate was introduced for four days intoa CO₂ atmosphere having a pressure of 600 hPa at a temperature of 80° C.In one case the TEMA acetate comprised included a surplus of water whilein the other case no water was added. The water content of the sampleincluding water increased from 10% to 35% while the sample without waterincreased only from 10% to 15%. After the four days acid was added tothe two samples which lead to a clear generation of foam or gas in thesample without water, while the reaction of the probe with water wasless intense. Thus, the water may lead to a reduced CO₂ sorption of theionic liquid.

In the following two examples will be described whereintrioctylmethylammonium (TOMA)-acetylacetonate or -acetate is used tosorp a gas having an electric multipole moment.

Example 1 Sorption of Hydrogen Sulphide

The experiment was performed at room temperature and a vapor pressureequilibrium of 338 hPa. A beaded bottle is flushed with 120 ml ofhydrogen sulphide by using two needles. One of the needles is connectedto a manometer having a resolution of 1 hPa. Subsequently 1 ml ofTOMA-acetate is injected into the bottle by using one of the needles,wherein the TOMA-acetate was preheated by a hairdryer in order to reducethe viscosity. After 30 minutes of stirring by using a magnetic stir bara constant reduction of the pressure of 622 hPa was observed. Thispressure reduction corresponds to a molar ratio of 0.26moI_(H2S)/mol_(IL) at an equilibrium pressure of 338 hPa. Forcomparison, a 30% aqueous solution of monoethanolamine provides, underthe same conditions, a pressure reduction of 651 hPa which correspondsto a molare ratio of 0.11 mol_(H2S)/mol_(L) at an equilibrium pressureof 309 hPa.

Example 2 Sorption of Carbon Dioxide

The experiment was performed at room temperature and a vapor pressureequilibrium of 523 hPa. A beaded bottle is flushed with 120 ml of carbondioxide by using two needles. One of the needles is connected to amanometer having a resolution of 1 hPa. Subsequently 1 ml ofTOMA-acetylacetonate is injected into the bottle by using one of theneedles, wherein the TOMA-acetylacetonate was preheated by a hairdryerin order to reduce the viscosity. After 30 minutes of stirring by usinga magnetic stir bar a constant reduction of the pressure of 437 hPa wasobserved. This pressure reduction corresponds to a molar ratio of 0.18mol_(CO2)/mol_(IL) at an equilibrium pressure of 523 hPa. Forcomparison, a 30% aqueous solution of monoethanolamine provides, underthe same conditions, a pressure reduction of 670 hPa which correspondsto a molare ratio of 0.12 mol_(CO2)/mol_(L) at an equilibrium pressureof 290 hPa.

Finally, it should be noted that the above-mentioned embodimentsillustrate rather than limit the invention, and that those skilled inthe art will be capable of designing many alternative embodimentswithout departing from the scope of the invention as defined by theappended claims. In the claims, any reference signs placed inparentheses shall not be construed as limiting the claims. The word“comprising” and “comprises”, and the like, does not exclude thepresence of elements or steps other than those listed in any claim orthe specification as a whole. The singular reference of an element doesnot exclude the plural reference of such elements and vice-versa. In adevice claim enumerating several means, several of these means may beembodied by one and the same item of software or hardware. The mere factthat certain measures are recited in mutually different dependent claimsdoes not indicate that a combination of these measures cannot be used toadvantage.

1. A method comprising: using an ionic liquid for sorption of a gashaving an electric multipole moment, wherein the ionic liquid comprisesan anion and a non-aromatic cation.
 2. The method according to claim 1,wherein the non-aromatic cation is an aliphatic cation.
 3. The methodaccording to claim 1, wherein the non-aromatic cation is a quaternarymaterial.
 4. The method according to claim 1, wherein the gas is one outof the group consisting of: H₂O, HCN, H₂S, H₂Se, H₂Te, CO₂, CO, CS₂,COS, CF₂O, CF₂S, O₃, NO, NO₂, N₂O, N₂O₃, NOCl, NF₃, HNO₂, HNO₃, RCOR′,RCOH, RCOOH, CF₃SO₃H, CF₃COOH, RCOOR′, ROH, ROR, RSH, RSR, ROCl, ROBr,RONH₂, RONHR′, RONR′R″, RSO₂Cl, RSO₂Br, ROCN, RCON, RCN, HF, HCl, HBr,HI, SO₂, SO₃, NH₃, NH₂R, NHR′R″, NR′R″R′″, PH₃, PH₂R, PHR′R″, PR′R″R′″,BF₃, BCl₃, BBr₃, B₂H₆, BrF₃, ClF₃, ClF₅, ClCN, IF₅, AsH₃, CH₃F, CH₃Cl,CH₃Br, CH₃I, POCl₂, PSCl₂, PF₅, SF₄, SF₆, SO₂F₂, SO₂Cl₂, SOCl, H₂C═CHBr,H₂C═CHCl and ethylene oxide.
 5. The method according to claim 4, whereinat least one of R, R′, R″ and/or R′″ is a moiety out of the groupconsisting of: C₁-C₈-alkyl, alkenyl, alkinyl, cycloalkyl, cycloalkenyl,aryl and heteroaryl.
 6. The method according to claim 1, wherein theanion comprises a carbonate, an alkylcarbonate, an arylcarbonate acarboxylate, a carbanion, and/or an aromatic compound.
 7. The methodaccording to claim 1: wherein the ionic liquid satisfies the genericformula [Q⁺][A⁻], wherein the anion is described by one of the followingstructures:


8. The method according to claim 1, wherein the ionic liquid satisfiesthe generic formula [Q⁺]_(a)[A^(a-)], wherein [A^(a-)] with the chargea-, is selected out of the group consisting of: dialkyl ketones,dialkyl-1,3-diketones, alkyl-β-keto esters, terminal alkines, linear orcyclic 1,3-thioethers, dialkyl phosphonates, dialkyl malonic acidesters, β-cyano carbonic acids and their respective alkylesteres,β-alkoxy carbonic acids and their respective alkylesters, β-cyanonitriles, cyclopentadiene (substituted if necessary), trialkylimines,dialkylimines, diaryl ketones, alkyl-aryl-ketones, diaryl-1,3-diketones,alkyl-aryl-1,3-diketones, β-aryloxy carbonic acids and their respectivealkylesters, β-aryloxy carbonic acids and their respective arylesters,aryl-β-ketoesters, diarylphosphonates, alkyl-aryl-phosphonates, diarylmalonic acid esters, alkyl-aryl-malonic acid esters, β-cyano carbonicacids arylesters and arylimines.
 9. The method according to claim 1,wherein the ionic liquid satisfies the generic formula [Q⁺]_(a)[A^(a-)],wherein [A^(a-)] is a carbanion formed by deprotonating a chemicalcompound out of the group consisting of: acetoacetic ester, malonicmononitrile, malonic acid dimethylester, malonic acid diethylester,acetylacetone, malonic acid dinitrile, acetone, diethylketone,methlethylketone, dibutylketone, 1,3-dithian, acetaldehyde,benzaldehyde, crotonaldehyde and butyraldehyde.
 10. The method accordingto claim 1, wherein the anion comprises at least one polar group. 11.The method according to claim 1, wherein the cation is a quaternary orprotonated cation out of the group consisting of: ammonium, phosphonium,sulfonium, piperidinium, pyrrolidinium, and morpholinium.
 12. The methodaccording to claim 1, wherein the cation is one out of the groupconsisting of: trialkylmethylammonium, tetramethylammonium,triethylmethylammonium, tributylmethylammonium, trio ctylmethylammoniumtrialkylammonium, trimethylammonium, triethylammonium, tributylammonium,and trioctylammonium.
 13. The method according to claim 1, wherein thecation is one out of the group consisting of: tetramethylammonium,triethylmethylammonium, tributylmethylammonium, and trioctylmethylammonium.
 14. The method according to claim 1, wherein theanion is written in the form [RCO₂ ⁻], wherein [RCO₂ ⁻] is one out ofthe group consisting of: carboxylate, formiate, acetate, propionate,butyrate, benzoate, and salicylate.
 15. The method according to claim 1,wherein the anion is written in the form [RCO₂ ⁻], wherein [RCO₂ ⁻] is acarboxylate wherein R is a radical out of the group consisting of:C₁-C₃₀-alkyl, C₃-C₁₂-cycloalkyl, C₂-C₃₀-alkenyl, C₃-C₁₂-cycloalkenyl,C₂-C₃₀-alkinyl, aryl and heteroaryl.
 16. The method according to claim1, wherein the anion is written in the form [RCO₂], wherein [RCO₂ ⁻] isa carboxylate wherein R represents one to three radicals out of thegroup consisting of: C₁-C₆-alkyl, aryl, heteroaryl, C₃-C₇-cycloalkyl,halogen, cyanide, ORc, SRc, NRcRd, CORc, COORc, CO—NRcRd, wherein Rcand/or Rd, is one of the group consisting of: hydrogen, C₁-C₆-alkyl,C₁-C₆-halogenalkyl, cyclopentyl, cyclohexyl, phenyl, tolyl, and benzyl.17. The method according to claim 1, wherein the gas is CO₂.
 18. Themethod according to claim 17, wherein CO₂ is sorbed from a medium whichis selected out of the group consisting of: recovery gas, synthesis gas,water gas, inhaled air, and exhaled air.
 19. A device for sorption of agas having an electric multipole moment, the device comprising: areservoir of an ionic liquid comprising an anion and a non-aromaticcation.
 20. The device according to claim 19, wherein the device is aheat pump, and wherein the heat pump comprises a circuit including CO₂and the ionic liquid comprises an anion and a non-aromatic cation asworking media.
 21. A method comprising: using an ionic liquid forsorption of a gas having an electric multipole moment, wherein the ionicliquid comprises a carbanion and a cation.
 22. The method according toclaim 21, wherein the ionic liquid satisfies the generic formula[Q⁺]_(a)[A^(a-)], wherein [Q]⁺ is one out of the group consisting ofquaternary ammonium cation [R^(1′)R¹R²R³N]⁺, phosphonium[R^(1′)R¹R²R³P]⁺, sulfonium [R^(1′)R¹R²S]⁺ and a hetero aromatic cation.